Solid-state imaging device and method for producing the same

ABSTRACT

A solid-state imaging device includes a semiconductor substrate, a light shielding section having an aperture for partially shielding light incident on a surface of the semiconductor substrate, a light reception section for converting the light which is incident on the surface of the semiconductor substrate through the aperture to an electric charge, and a passivation section having a substantially flat top surface and overlying the light shielding section, the light reception section and the aperture.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a solid-state imaging device,and in particular to a solid-state imaging device structured so as toenhance the sensitivity of a light reception section thereof and amethod for producing such a device.

[0003] 2. Description of the Related Art

[0004] In recent years, the transmission and reception of images isbecoming indispensable to portable information devices and the likeincluding cellular phones. So-called solid-state imaging devices such asCCDs are used for imaging purposes while liquid crystal panels are usedfor displaying images. In the field of solid-state imaging devices, CMOSimage sensors based on a so-called CMOS logic process, which istypically used for producing a normal integrated circuit, are widelydeveloped with a view to achieving low power consumption and a low cost.As in the case of CCDs, the demand for higher resolution andminiaturization has necessitated CMOS image sensors having reduced pixelsize, as well as having a reduced area of the light reception section,and reduced aperture size in a light shielding film. However, since CMOSimage sensors have so far been developed based on the so-called logicprocess, very little attention has been paid to the opticalcharacteristics of CMOS image sensors, such as reflection or refractionat interfaces between the layers of multi-layered films incorporatedtherein. Therefore, it is difficult with CMOS image sensors toefficiently converge incident light and obtain sufficient sensitivity.

[0005] A conventional solid-state imaging device, in particular a CMOSimage sensor, will be described with reference to FIG. 5. A lightreception section 12 is formed on a top surface of a silicon substrate11 for converting incident light (hν) to an electric charge. Aninterlaminar insulation film 13 is formed on the silicon substrate 11for electrically isolating a first metal layer 18, a second metal layer19, and a light shielding film 14 from one another. The light shieldingfilm 14 is formed so as not to overlie a light reception face of thelight reception section 12, so that light incident on the interlaminarinsulation film 13 does not fall anywhere except the light receptionsection 12. A passivation film 15 is formed on the light shielding film14 and on the interlaminar insulation film 13 which is present within anaperture of the light shielding film 14. The passivation film 15provides moisture-resistance, chemical resistance, and improved barrierproperties against impurities such as Na ions, oxygen, etc., and metals.A planarization film 16 is formed on the passivation film 15. Amicrolens 17 is formed for converging light which is incident on theplanarization film 16. As the interlaminar insulation film 13, adeposited film such as a P (plasma CVD)—SiO₂ film, an NSG film (asilicon oxide film containing no impurities), a BPSG film (a siliconoxide film containing phosphorus and boron) or the like is used. As thepassivation film 15, a monolayer film, such as a P (plasma CVD)—SiNfilm, or a deposited film composed of a P—SiN film and a PSG film (asilicon oxide film containing phosphorus), is generally used. Theplanarization film 16 is generally composed of an acrylic material. Inthe case of a color solid-state imaging device, an acrylic material anda color filter are utilized as the planarization film 16. Inconventional CMOS image sensor structures, the passivation film 15 has astepped portion as described above, which prevents the convergence oflight. When such a structure is adapted for higher resolution andminiaturization, the stepped portion of the passivation film 15 causes adecrease in the amount of light converged on the light reception section12, thereby making it difficult to obtain sufficient sensitivity.

[0006] A method for producing the above-described device will now bedescribed with reference to FIG. 6. The light reception section 12 isformed in the silicon substrate 11 through ion implantation, heattreatment, etc. After forming a polycrystalline silicon film and asilicide film on the silicon substrate 11 by using a CVD technique, agate electrode (not shown) is formed by patterning, etching, or thelike. Thereafter, a BPSG film is deposited as the interlaminarinsulation film 13 by a CVD technique. When the BPSG film receives heattreatment at a high temperature, the film becomes fluid so that itssurface can be flattened. By taking advantage of such characteristics ofthe BPSG film, the surface of the BPSG film is flattened so as tofacilitate the formation of the first metal layer 18. The first metallayer 18 is formed by depositing TiN, Al or the like on the BPSG film byusing a sputtering or CVD technique. Upon the first metal layer 18, theP—SiO₂ film is deposited as the interlaminar insulation film 13 by usinga CVD technique and the surface thereof is flattened by chemical machinepolishing. Thereafter, as in the case of the first metal layer 18, athin film of TiN, Al, or the like is formed as the second metal layer 19by using a sputtering or CVD technique. Similarly, upon the second metallayer 19, a P—SiO₂ film is deposited as the interlaminar insulation film13 by using a CVD technique and the surface thereof is flattened by thechemical machine polishing. Thereafter, TiN, Al, or the like isdeposited as the light shielding film 14 by using a sputtering or CVDtechnique, and the resultant film is patterned and etched so as not tooverlie the light reception section 12. Upon the light shielding film14, a P—SiN film is deposited as the passivation film 15 by using a CVDtechnique or the like. The planarization film 16 is formed by applyingan acrylic material to the passivation film 15. In the case of a colorsolid-state imaging device, an acrylic material is applied; a colorfilter is formed; and then the acrylic material is further appliedthereto as a protection coating, thereby completing the planarizationfilm 16. Thereafter, a lens material is applied and the microlens 17 isformed by patterning and heat treatment.

[0007] In a conventional solid-state imaging device shown as FIG. 5A,the refractive index of the P—SiN film used for the passivation film 15is about 2.0 while the refractive index of the acrylic material used forthe planarization film 16 is about 1.5 to 1.6. In the case where therefractive index of the passivation film 15 is higher than that of theplanarization film 16, when light falls onto an edge of the passivationfilm 15, the incident light is not converged on the light receptionsection 12 but rather refracted so as to travel outside the lightreception section 12 toward the first metal layer 18 or the second metallayer 19 since the edge of the passivation film 15 has a rounded shape.As shown in an enlarged view of FIG. 5B, when light falls onto the flattop surface of the stepped portion, total internal reflection can occurat an interface between the planarization film 16 and a face of thepassivation film 15 parallel to a side face of the light shielding film14, depending on the incident angle of the light, since the refractiveindex of the passivation film 15 is higher than that of theplanarization film 16. The incident light passes along the face of thepassivation film 15 parallel to the side face of the light shieldingfilm 14 so that the light is not converged on the light receptionsection 12. As described above, in the conventional structure shown asFIG. 5A, any light incident on a portion of the passivation film 15neighboring the side face of the light shielding film 14 is notconverged on the light reception section 12. Therefore, the effectiveaperture size of the light shielding film 14 is smaller than the actualaperture size by an amount corresponding to the thickness of thepassivation film 15.

[0008] The light reception face of the light reception section 12 usedto be sufficiently large relative to the stepped portion of thepassivation film 15. However, due to the reduced pixel size which isnecessitated for improved resolution and miniaturization, the lightreception face of the light reception section 12 is becoming smaller andthe aperture of the light shielding film 14 is also becoming narrower.Therefore, the ratio of the amount of light incident on the steppedportion of the passivation film 15 to the amount of light incident onthe aperture of the light shielding film 14 increases, thereby making itdifficult to obtain sufficient sensitivity. However, the passivationfilm 15 can not be omitted because the passivation film 15 plays animportant role in providing moisture-resistance, chemical resistanceand/or improved barrier properties against impurities such as Na ions,oxygen, etc., and metals.

[0009] The effect of the stepped portion of the passivation film 15 onthe numerical aperture of the light shielding film 14 will now bedescribed in detail. Provided that the sensitivity deteriorates by anamount corresponding to the thickness of the passivation film 15, theaperture size can be represented as (pixel size)−(width of the lightshielding film)−(2×thickness of the passivation film 15). For example,in the case where the width of the light shielding film 14 is 1.5 μm,and the thickness of the passivation film 15 is 0.5 μm, given a pixelsize of 10 μm×10 μm, the aperture of the light shielding film 14 iscalculated to be 10−1.5−(0.5×2)=7.5 μm, and therefore, the numericalaperture is 75%. Similarly, given a pixel size of 5 μm×5 μm, theaperture of the light shielding film 14 is calculated to be5−1.5−(0.5×2)=2.5 μm, and therefore, the numerical aperture is 50%.Starting from the above one-dimensional calculation, it will be seenthat the numerical aperture area as calculated in a two-dimensionalmanner gives rise to an even greater difference in the size (area)between the aperture and each pixel. The reduction in the numericalaperture of the light shielding film 14 is highly detrimental to theratio of light incident on the light reception face of the lightreception section 12; this effect is more detrimental than any reductionin the numerical aperture of layers below the light shielding film 14.

SUMMARY OF THE INVENTION

[0010] According to one aspect of this invention, there is provided asolid-state imaging device, including a semiconductor substrate, a lightshielding section having an aperture for partially shielding lightincident on a surface of the semiconductor substrate, a light receptionsection for converting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge, anda passivation section having a substantially flat top surface andoverlying the light shielding section, the light reception section andthe aperture.

[0011] According to one embodiment of the invention, the passivationsection includes at least a silicon nitride-based monolayer film.

[0012] According to another embodiment of the invention, a solid-stateimaging device further includes an insulation section having asubstantially flat top surface which is interposed between thepassivation section and the light shielding section.

[0013] According to still another embodiment of the invention, theinsulation section includes at least a silicon oxide-based monolayerfilm.

[0014] According to another aspect of the invention, there is provided amethod for producing a solid-state imaging device which includes asemiconductor substrate, a light shielding section having an aperturefor partially shielding light incident on a surface of the semiconductorsubstrate, a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge, and a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture, and the methodincludes the steps of forming a thin film used for forming thepassivation section on the light shielding section and the aperture, andflattening a surface of the thin film to form the passivation section bychemical machine polishing.

[0015] According to still another aspect of the invention, there isprovided a method for producing a solid-state imaging device whichincludes a semiconductor substrate, a light shielding section having anaperture for partially shielding light incident on a surface of thesemiconductor substrate, a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge, and a passivation sectionhaving a substantially flat top surface and overlying the lightshielding section, the light reception section and the aperture, and themethod includes the steps of forming a thin film used for forming thepassivation section on the light shielding section, applying an SOG filmto the thin film used for forming the passivation section, andperforming an etchback technique under a condition that a selectiveratio of the SOG film to the thin film used for forming the passivationsection is about 1 to 1.

[0016] According to still another aspect of the invention, there isprovided a method for producing a solid-state imaging device whichincludes a semiconductor substrate, a light shielding section having anaperture for shielding light incident on a surface of the semiconductorsubstrate, a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge, a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture, and an insulationsection having a substantially flat top surface which is interposedbetween the passivation section and the light shielding section, and themethod includes the steps of forming the insulation section on the lightshielding section, flattening a surface of the insulation section bychemical machine polishing, and forming the passivation section so as tohave the substantially flat top surface by depositing a material usedfor forming the passivation section on the insulation section.

[0017] According to still another aspect of the invention, there isprovided a method for producing a solid-state imaging device whichincludes a semiconductor substrate, a light shielding section having anaperture for partially shielding light incident on an surface of thesemiconductor substrate, a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge, a passivation section havinga substantially flat top surface and overlying the light shieldingsection, a light reception section and the aperture, and an insulationsection having a substantially flat top surface which is interposedbetween the passivation section and the light shielding section, and themethod includes the steps of forming the insulation section so as tohave the substantially flat top surface by applying an SOG film to thelight shielding section and the aperture, and forming the passivationsection so as to have the substantially flat top surface by depositing amaterial used for forming the passivation section on the insulationsection.

[0018] In order to achieve the above-described objectives, according tothe present invention, a passivation film is deposited on aninterlaminar insulation film so as to have a thickness which is greaterthan that of a light shielding film. Thereafter, a portion of thethickly deposited passivation film is removed, to such an extent thatthe light shielding film is not exposed, by chemical machine polishingor by using an etchback technique after applying an SOG to thepassivation film. Thus, a surface of the passivation film is flattened.

[0019] Alternatively, a silicon oxide-based insulation film is thicklydeposited on the light shielding film and the interlaminar insulationfilm in the manner described above. Thereafter, a portion of theresultant film is removed, to such an extent that the light shieldingfilm is not exposed, by using chemical machine polishing. Thus, asurface of the film is flattened. A passivation film is then depositedon a top surface of the silicon oxide-based insulation film. Since thetop surface of the silicon oxide-based insulation film is flat, the topsurface of the passivation film, which is deposited on the insulationfilm, also becomes flat. Therefore, the passivation film is preventedfrom having any stepped portion, which is one problem associated with aconventional passivation film.

[0020] Alternatively, an SOG film is applied on the light shielding filmand the interlaminar insulation film. The passivation film is thendeposited on a top surface of the SOG film. Since the top surface of theSOG film is flat, the top surface of the passivation film, which isdeposited on the SOG film, also becomes flat. Therefore, the passivationfilm is prevented from having any stepped portion, which is one problemassociated with a conventional passivation film.

[0021] As described above, through the use of the aforementionedtechniques, according to the present invention, the passivation film isprevented from having any stepped portion, which is one problemassociated with a conventional passivation film. Therefore, a componentof light which would otherwise fall onto stepped areas to be refractedin directions away from the light reception section can be converged onthe light reception section. Thus, the imaging device according to thepresent invention can be adapted for higher resolution andminiaturization.

[0022] Thus, the invention described herein makes possible theadvantages of: (1) providing a solid-state imaging device which canconverge incident light on a light reception section thereof due to theabsence of stepped portions on a passivation film; and (2) providing amethod for producing such a solid-state imaging device.

[0023] These and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a cross-sectional view of a solid-state imaging deviceaccording to Example 1 of the present invention.

[0025]FIG. 2 is a cross-sectional view of a solid-state imaging deviceaccording to Example 2 of the present invention.

[0026]FIGS. 3A, 3B, 3C, 3D, 3E, and 3F are cross-sectional viewsillustrating production steps of a solid-state imaging device accordingto Example 1 of the present invention.

[0027]FIGS. 4A, 4B, 4C, 4D, 4E, 4F and 4G are cross-sectional viewsillustrating production steps of a solid-state imaging device accordingto Example 2 of the present invention.

[0028]FIG. 5A is a cross-sectional view illustrating a structure of aconventional solid-state imaging device.

[0029]FIG. 5B is a partial enlarged view of FIG. 5A.

[0030]FIGS. 6A, 6B, 6C, 6D, 6E, and 6F are cross-sectional viewsillustrating production steps of a conventional solid-state imagingdevice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Examples of the present invention will be described below indetail with reference to drawings.

EXAMPLE 1

[0032] A basic structure of Example 1 of the present invention is shownin FIG. 1. As shown in FIG. 1, a light reception section 2 forconverting incident light to an electric charge is formed on a topsurface of a silicon substrate 1. An interlaminar insulation film 3 forelectrically isolating a first metal layer 8, a second metal layer 9,and a light shielding film 4 from one another is formed on the siliconsubstrate 1. The light shielding film 4 is formed on the interlaminarinsulation film 3 without overlying, a light reception face of the lightreception section 2, so that incident light does not fall anywhereexcept the light reception section 2. A passivation film 5 is formed onthe light shielding film 4 and on the interlaminar insulation film 3which is present within an aperture of the light shielding film 4 inorder to provide moisture-resistance, chemical resistance, and improvedbarrier properties against impurities such as Na ions, oxygen, etc., andmetals. A portion of the passivation film 5 is removed, to such anextent that the light shielding film 4 is not exposed, by using chemicalmachine polishing or an etchback technique. Thus a surface of thepassivation film is flattened. A planarization film 6 is formed on thepassivation film 5. A microlens 7 is formed for converging light whichis incident on the planarization film 6. In Example 1, the passivationfilm 5 may be in the form of a SiN-based monolayer film, or a depositedfilm composed of a SiN-based film, having a refractive index of about2.0. An acrylic material is used for the planarization film 6, having arefractive index of about 1.5 to 1.6.

[0033] In conventional structures, the passivation film 15 would have astepped portion as shown in FIGS. 5A and 5B. Light incident on thestepped portion is refracted in directions away from the light receptionsection, due to the different refractive index of an edge of the steppedportion. Since the refractive index of the passivation film 15 is higherthan that of the planarization film 16, total internal reflection occursat an interface between the planarization film 16 and a face of thepassivation film 15 parallel to a side face of the light shielding film14, so that incident light is not converged on the light receptionsection 12. However, in the structure according to Example 1 of thepresent invention, the passivation film 5 is thickly deposited and a topsurface thereof is flattened by chemical machine polishing or anetchback technique, so that any refraction of incident light associatedwith a stepped portion, as in the case of the passivation film 15 ofconventional structures, does not occur. As a result, most of lightconverged by the microlens 7 is converged on the light reception section2.

[0034] A method for producing a solid-state imaging device according toExample 1 of the present invention will now be described with referenceto FIGS. 3A, 3B, 3C, 3D, 3E, and 3F. The light reception section 2 isformed in the silicon substrate 1 through ion implantation, heattreatment, etc. (FIG. 3A). After forming a polycrystalline silicon filmand a silicide film on the silicon substrate 1 by using a CVD technique,a gate electrode (not shown) is formed by patterning, etching, or thelike. Thereafter, a BPSG film is deposited so as to have a thickness ofabout 5000 Å to 15000 Å as the interlaminar insulation film 3 by a CVDtechnique. By subjecting the BPSG film to heat treatment at about 850 to950° C., its surface is flattened so as to facilitate the formation ofthe first metal layer 8. The first metal layer 8 is formed by depositingTiN to a thickness of about 300 Å to 1000 Å and Al to a thickness ofabout 3000 Å to 10000 Å on the BPSG film by using a sputtering or CVDtechnique (FIG. 3B). Upon the first metal layer 8, a P—SiO₂ film havinga thickness of about 20000 Å to 25000 Å is deposited as the interlaminarinsulation film 3 by using a CVD technique, and a thickness of about10000 Å is removed from the resultant film by chemical machinepolishing, thereby flattening the film surface. Thereafter, as in thecase of the first metal layer 8, TiN having a thickness of about 300 Åto 1000 Å and Al having a thickness of about 3000 Å to 10000 Å aredeposited as the second metal layer 9 by using a sputtering or CVDtechnique (FIG. 3C). Similarly, upon the second metal layer 9, a P—SiO₂film having a thickness of about 20000 Å to 25000 Å is deposited as theinterlaminar insulation film 3 by using a CVD technique and a thicknessof about 10000 Å is removed from the resultant film by chemical machinepolishing, thereby flattening the film surface. Thereafter, TiN having athickness of about 300 Å to 1000 Å and Al having a thickness of about3000 Å to 10000 Å are deposited as the light shielding film 4 by using asputtering or CVD technique, and the resultant film is patterned andetched so as not to overlie the light reception section 2 (FIG. 3D).Upon the light shielding film 4, a P—SiN film having a thickness of20000 Å is deposited as the passivation film 5. Thereafter, a thicknessof about 10000 Å is removed from the P-SiN film by chemical machinepolishing, thereby flattening the film surface (FIG. 3E). In another wayof flattening, conventional production steps are used so as to form thelight shielding film 4, and thereafter, a P-SiN layer is thicklydeposited as the passivation film 5 by using a CVD technique or thelike.

[0035] Thereafter, SOG is applied to a top surface of the passivationfilm 5 and a top surface of the resultant film is etched by using an RIEunder an etching condition such that the selectivity ratio of the P-SiNto the SOG is about 1:1, thereby flattening the top surface of thepassivation film 5. More particulaly, the light shielding film 4 isdeposited so as to have a thickness of about 3000 Å to 10000 Å, and aP—SiN film having a thickness of about 20000 Å is deposited as thepassivation film 5. SOG is applied to the P—SiN film so as to have athickness of about 15000 Å. A 1:1 selectivity ratio of P—SiN to SOG canbe obtained under the following RIE etching conditions: pressure: 4 to15 Pa; CHF₃: 20 to 50 sccm; CF₄: 20 to 50 sccm; Ar: 50 to 100 sccm: O₂:1 to 5 sccm; and RF: 200 to 700 W. By performing etching under suchconditions, the top surface of the P—SiN film can be flattened (FIG.3E). After flattening the top surface of the passivation film 5, aplanarization film 6 is formed by applying an acrylic material to thepassivation film 5. In the case of a color solid-state imaging device,an acrylic material is applied; a color filter is formed; and then theacrylic material is further applied thereto as a protection coating,thereby completing the planarization film 6. Thereafter, a lens materialis applied to the planarization film 6, and the microlens 7 is formed bypatterning and heat treatment (FIG. 3F).

[0036] Since the stepped portions of the passivation film 5 areeliminated, the aperture of the light shielding film 4 can berepresented as (pixel size)−(width of light shielding film). Forexample, in the case where the width of the light shielding film 4 is1.5 μm, given a pixel size of 5 μm×5 μm, the aperture of the lightshielding film 4 is calculated to be 5−1.5=3.5 μm, and therefore, thenumerical aperture is 70%. Since the conventional numerical aperture is50%, the numerical aperture of the present example is improved so as tobe 1.4 times the conventional numerical aperture.

EXAMPLE 2

[0037] Example 2 of the present invention will now be described.

[0038] A basic structure of Example 2 of the present invention is shownin FIG. 2. As shown in FIG. 2, a light reception section 2 forconverting incident light to an electric charge is formed on a topsurface of a silicon substrate 1. An interlaminar insulation film 3 forelectrically isolating a first metal layer 8, a second metal layer 9,and a light shielding film 4 from one another is formed on the siliconsubstrate 1. The light shielding film 4 is formed on the interlaminarinsulation film 3 without overlying a light reception face of the lightreception section 2, so that incident light does not fall anywhereexcept the light reception section 2. A silicon oxide film 10 is formedon the light shielding film 4 and on the interlaminar insulation film 3which is present within an aperture of the light shielding film 4. Aportion of the silicon oxide film 10 is removed, to such an extent thatthe light shielding film 4 is not exposed, by using chemical machinepolishing. Thus a surface of the silicon oxide film 10 is flattened.When the silicon oxide film 10 is formed by application of SOG, asilicon oxide film having a flat top surface can be formed withoutperforming chemical machine polishing. A passivation film 5 is formed onthe silicon oxide film 10 in order to provide moisture-resistance,chemical resistance, and improved barrier properties against impuritiessuch as Na ions, oxygen, etc., and metals. A planarization film 6 isformed on the passivation film 5. A microlens 7 is formed for converginglight which is incident on the planarization film 6.

[0039] In Example 2, because it is more advantageous to flatten the topsurface of the silicon oxide-based film than to flatten the top surfaceof the P—SiN film, it is easier to apply chemical machine polishing tothe silicon oxide film 10 than to the P—SiN passivation film 5 for thefollowing reasons. Firstly, a silicon oxide-based film can be relativelyeasily etched since its etching rate is faster than that of the P—SiNfilm. Secondly, since chemical machine polishing is performed at thetime of forming the interlaminar insulation film 3, a conventionalchemical machine polishing technique can be applied to the siliconoxide-based film. Since the passivation film 5 is deposited on thesilicon oxide film 10 after the top surface of the silicon oxide film 10is flattened, a top surface of the passivation film 5 can also beflattened. Thus, the stepped portion of the passivation film 5 shown inFIG. 5A can be eliminated, so that light which is converged by themicrolens 7 on the light reception section 2 can be converged withoutbeing obstructed.

[0040] A method for producing a solid-state imaging device according toExample 2 will now be described with reference to FIG. 4. Productionsteps of the conventional method and Example 1 are used in Example 2 soas to form the light shielding film 4. The light reception section 2 isformed in the silicon substrate 1 through ion implantation, heattreatment, etc. (FIG. 4A). After forming a polycrystalline silicon filmand a suicide film on the silicon substrate 1 by using a CVD technique,a gate electrode (not shown) is formed by patterning, etching, or thelike. Thereafter, a BPSG film having a thickness of about 5000 Å to15000 Å is deposited as the interlaminar insulation film 3 by a CVDtechnique. By subjecting the BPSG film to heat treatment at about 850 to950° C., its surface is flattened so as to facilitate the formation ofthe first metal layer 8. The first metal layer 8 is formed by depositingTiN to a thickness of about 300 Å to 1000 Å and Al to a thickness ofabout 3000 Å to 10000 Å on the BPSG film by using a sputtering or CVDtechnique (FIG. 4B). Upon the first metal layer 8, a P—SiO₂ film havinga thickness of about 20000 Å to 25000 Å is deposited as the interlaminarinsulation film 3 by using a CVD technique, and a thickness of about10000 Å is removed from the P—SiN film by chemical machine polishing,thereby flattening the film surface. Thereafter, as in the case of thefirst metal layer 8, TiN having a thickness of about 300 Å to 1000 Å andAl having a thickness of about 3000 Å to 10000 Å are deposited as thesecond metal layer 9 by using a sputtering or CVD technique (FIG. 4C).Similarly, upon the second metal layer 9, a P—SiO₂ film having athickness of about 20000 Å to 25000 Å is deposited as the interlaminarinsulation film 3 by using a CVD technique, and a thickness of about10000 Å is removed from the P—SiO₂ film by chemical machine polishing,thereby flattening the film surface. Thereafter, TiN having a thicknessof about 300 Å to 1000 Å and Al having a thickness of about 3000 Å to10000 Å are deposited as the light shielding film 4 by using asputtering or CVD technique, and the resultant film is patterned andetched so as not to overlie the light reception section 2 (FIG. 4D). Asdescribed above, production steps of the conventional method are used soas to form the light shielding film 4. Thereafter, the silicon oxidefilm 10 having a thickness of about 20000 Å to 25000 Å is deposited byusing a CVD technique and a thickness of about 10000 Å is removed fromthe resultant film by a chemical machine polishing (FIG. 4E).Thereafter, a P—SiN film 5 having a thickness of about 3000 Å to 10000 Åis deposited on the silicon oxide film 10, thereby flattening a topsurface of the P—SiN film 5 (FIG. 4F).

[0041] In another way of flattening, conventional production steps areused so as to form the light shielding film 4, and thereafter, SOG isapplied to the light shielding film 4 as the silicon oxide film 10 (FIG.4E). A P—SiN film 5 is deposited on the flattened silicon oxide film 10,which is formed of an SOG film, so as to obtain the P—SiN film 5 havinga flat top surface (FIG. 4F). In this case, the applied SOG film has athickness of about 10000 Å to 15000 Å, and the P—SiN film 5 having athickness of about 3000 Å to 10000 Å is deposited by a CVD technique.Thereafter, the planarization film 6 is formed by applying an acrylicmaterial to the P—SiN film 5. In the case of a color solid-state imagingdevice, an acrylic material is applied; a color filter is formed; andthen the acrylic material is further applied thereto as a protectioncoating, thereby completing the planarization film 6. Thereafter, a lensmaterial is applied thereto and the microlens 7 is formed by patterningand heat treatment (FIG. 4G).

[0042] As described above, according to the present invention, thestepped portion can be eliminated by flattening a top surface of thepassivation film, so that incident light can be converged on the lightreception section. Therefore, the present invention makes it possible toprovide a solid-state imaging device which is capable of efficientlyconverging incident light on a light reception section thereof so as tobe adapted for reduced pixel size.

[0043] Various other modifications will be apparent to and can bereadily made by those skilled in the art without departing from thescope and spirit of this invention. Accordingly, it is not intended thatthe scope of the claims appended hereto be limited to the description asset forth herein, but rather that the claims be broadly construed.

What is claimed is:
 1. A solid-state imaging device, comprising: asemiconductor substrate; a light shielding section having an aperturefor partially shielding light incident on a surface of the semiconductorsubstrate; a light reception section for converting the light which isincident on the surface of the semiconductor substrate through theaperture to an electric charge; and a passivation section having asubstantially flat top surface and overlying the light shieldingsection, the light reception section and the aperture.
 2. A solid-stateimaging device according to claim 1 , wherein the passivation sectioncomprises at least a silicon nitride-based monolayer film.
 3. Asolid-state imaging device according to claim 1 , further comprising aninsulation section having a substantially flat top surface which isinterposed between the passivation section and the light shieldingsection.
 4. A solid-state imaging device according to claim 3 , whereinthe insulation section comprises at least a silicon oxide-basedmonolayer film.
 5. A method for producing a solid-state imaging device,wherein the device comprises: a semiconductor substrate; a lightshielding section having an aperture for partially shielding lightincident on a surface of the semiconductor substrate; a light receptionsection for converting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge; anda passivation section having a substantially flat top surface andoverlying the light shielding section, the light reception section andthe aperture, wherein the method comprises the steps of: forming a thinfilm used for forming the passivation section on the light shieldingsection and the aperture; and flattening a surface of the thin film toform the passivation section by chemical machine polishing.
 6. A methodfor producing a solid-state imaging device, wherein the devicecomprises: a semiconductor substrate; a light shielding section havingan aperture for partially shielding light incident on a surface of thesemiconductor substrate; a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge; and a passivation sectionhaving a substantially flat top surface and overlying the lightshielding section, the light reception section and the aperture, whereinthe method comprises the steps of: forming a thin film used for formingthe passivation section on the light shielding section; applying an SOGfilm to the thin film used for forming the passivation section; andperforming an etchback technique under a condition that a selectiveratio of the SOG film to the thin film used for forming the passivationsection is about 1:1.
 7. A method for producing a solid-state imagingdevice, wherein the device comprises: a semiconductor substrate; a lightshielding section having an aperture for shielding light incident on asurface of the semiconductor substrate; a light reception section forconverting the light which is incident on the surface of thesemiconductor substrate through the aperture to an electric charge; apassivation section having a substantially flat top surface andoverlying the light shielding section, the light reception section andthe aperture; and an insulation section having a substantially flat topsurface which is interposed between the passivation section and thelight shielding section, wherein the method comprises the steps of:forming the insulation section on the light shielding section;flattening a surface of the insulation section by chemical machinepolishing; and forming the passivation section so as to have thesubstantially flat top surface by depositing a material used for formingthe passivation section on the insulation section.
 8. A method forproducing a solid-state imaging device, wherein the device comprises: asemiconductor substrate; a light shielding section having an aperturefor partially shielding light incident on an surface of thesemiconductor substrate; a light reception section for converting thelight which is incident on the surface of the semiconductor substratethrough the aperture to an electric charge; a passivation section havinga substantially flat top surface and overlying the light shieldingsection, a light reception section and the aperture; and an insulationsection having a substantially flat top surface which is interposedbetween the passivation section and the light shielding section, whereinthe method comprises the steps of: forming the insulation section so asto have the substantially flat top surface by applying an SOG film tothe light shielding section and the aperture; and forming thepassivation section so as to have the substantially flat top surface bydepositing a material used for forming the passivation section on theinsulation section.